The present invention relates to the use of lysozyme gene structures in plants for increasing the resistance of plants to fungi and animal pests.
A large proportion of the world's harvest of crop plants is constantly destroyed by pests (in 1967, the potential crop loss was 35%; cf. Chemistry of Pesticides, edited by K. H. Buchel, John Wiley & Sons, New York, 1983, page 6). There is therefore an urgent demand to research into, and utilize, all possible means which are suitable for reducing, or preventing, the infestation of crop plants with pests.
Patent application WO 89/04371 describes the transformation of plants having specific lysozyme genes for increasing the resistance to specific bacteria.
It has now been found that an increased resistance of plants to fungi and animal pests can be achieved by introducing into the genome of the plants one or more (preferably one) lysozyme gene structures, which express lysozymes and which are characterized in that they consist of chimeric gene fusions of the TR promoter, the signal peptide sequence of barley alpha-amylase and one or more (preferably one) lysozyme genes or contain these chimeric gene fusions.
With the knowledge of the prior art, it was surprising and could not have been predicted that a particularly pronounced resistance of plants to pathogens could be achieved with the aid of the gene structures which can be used according to the invention.
The term lysozymes describes a group of enzymes EC 3.2.1.17, which occur in nature. Examples which may be mentioned are chicken albumin lysozyme and T4-phage lysozyme.
Lysozyme genes are understood as meaning any nucleic acid (DNA) which, after having been transcribed into RNA and translated into protein, effects (in a suitable environment) the formation of an enzyme which has the known properties of lysozymes.
The lysozyme gene structures or their components can contain other DNA sequences, for example, at their beginning and/or end, which do not hinder their function, or not to a great extent.
The lysozyme genes and the other components of lysozyme gene structures can be present in the same form as they are contained in the genome of the organism from which they originate ("genomic" form, including non-lysozyme-encoding and/or non-regulatory sequences (such as introns), or in a form which corresponds to cDNA ("copy" DNA), which can be obtained via mRNA with the aid of reverse-transcriptase/polymerase (and no longer contains introns).
In the lysozyme gene structures which can be used according to the invention, it is possible for DNA sequences to be replaced by other DNA sequences which act essentially in the same sense.
They can also have, at the ends, those DNA sequences which suit the particular manipulation of the genes (for example "linkers").
Preferred lysozyme gene structures which can be used according to the invention consist of, or contain, chimeric gene fusions which, in addition to the lysozyme gene(s), contain the TR promoter and the signal peptide sequence of barley alpha-amylase, as they occur in plasmid pSR 2-4.